Vehicles, such as aircraft, typically utilize one or more power distribution systems to distribute power from a primary power source to various vehicle systems. In aerospace, electrical power distribution SSPCs are used to switch the voltage from the power sources (e.g. generators or batteries) to the loads. Electronic switches are commonly used in place of mechanical relays to distribute power from the source to the load. A solid state power distribution system typically includes at least one electronic switching device, such as a field effect transistor (FET), and electronic circuitry that provides wiring protection. The electronic switching device and circuitry are usually built in semiconductor technology and therefore referred to as a solid state switching device (“SSSD”) and solid state power controller (“SSPC”). SSPCs have found widespread use because of their desirable status capability, reliability, and packaging density. SSPCs are gaining acceptance as a modern alternative to the combination of conventional electromechanical relays and circuit breakers for commercial aircraft power distribution due to their high reliability, “soft” switching characteristics, fast response time, and ability to facilitate advanced load management and other aircraft functions.
Electronics used in aerospace is exposed to neutron radiation because aircraft are flying at high elevation. Modern chip technologies become more and more susceptible to such phenomena, but not much is known. Commercially available electronic components available “of the shelf” are not even tested for this condition. Especially, highly integrated devices with very small structures, like microcontrollers, show that susceptibility. Particularly, so called Single Event Upsets (SEU) or Single Event Latch-ups (SEL) may put a microcontroller in a condition where the software stops running and the microcontroller falls into an inoperative condition.
In most modern SSPC applications for aerospace, commercially available “of the shelf” microcontrollers are used. In order to deal with neutron radiation susceptibility, a mechanism has been suggested to cycle control power to the microcontroller when it is latching up due to the neutron radiation. While this strategy works, it implies that the SSPC momentarily turns off. This is undesirable, as it may have an impact to the electric loads on the aircraft supplied by the SSPC.
Therefore, it would be beneficial to avoid any change in the output state of the SSPC during, or following, a Single Event Upset (SEU) or Single Event Latch-up (SEL).